The present invention relates to a venting valve for a liquid container, especially for a fuel tank of a working tool such as a motor chain saw, a cutter, a trimmer etc., having an internal combustion engine. The venting valve has a pressure compensation channel connected to the interior of the container which can be closed by a valve body seated sealingly on the valve seat. The valve body is lifted off the valve seat when vacuum is present in the interior of the container to thereby open the pressure compensation channel.
Venting valves for fuel tanks are known in many embodiments. For example, German Offenlegungsschrift 43 29 876 discloses a valve body which is comprised of rubber-elastic material and is shaped like a mushroom, whereby the outer edge of the mushroom head is sealingly positioned on the valve seat. In order to ensure venting of the interior of the container at minimal vacuum, the valve body must be embodied such that it is soft-elastic. However, this entails the problem that at greater vacuum the valve body will yield greatly and will be deformed so that leaks may occur.
Furthermore, the minimal closing forces of the mushroom-shaped valve body at normal pressure entail the risk that residues, foreign matter (dirt particles) etc., present on the valve seat, will prevent proper closing or opening of the mushroom-shaped valve body.
It is therefore an object of the present invention to improve a venting valve of the aforementioned kind such that it opens already at minimal vacuum to allow venting, while at high (excess) pressure it is reliably closed without mechanical overload.